1. Field of the Invention
The present invention relates to an electromagnetic wave filter at terahertz or infrared region using shape resonance and surface plasmon resonance in through-holes formed on a metallic layer and having various structures of periodic or random arrays.
2. Background of the Related Art
In general, in-depth research has been performed in order to improve transmission characteristics at visible light regions through surface plasmon on a metallic layer having a periodic through-hole array structure. In this structure, incident light transmits efficiently a through-hole having a size much smaller than half the wavelength.
In the recent years, study on these transmission characteristics has been expanded into infrared, terahertz and microwave regions. It has been known that the transmission resonance at these regions is closely related to not only surface wave on a metallic layer but a through-hole shape constituting a periodic structure. In practice, however, it is necessary to provide more comprehensive understanding as to how the resonance due to a through-hole shape is related to transmission characteristics, and how the transmission due to the shape resonance is characterized.